It is known that placing metal foam within a hollow structure, such as a tubular vehicle body component, can increase the crush resistance of the hollow structure.
Powder metal such as aluminum or zinc is mixed with a foaming agent such as Titanium Hydride (TiH2) and the mixture is compacted and placed within the hollow structure. The hollow structure is heated to in turn heat the mixture. Heating of the mixture causes melting of the powder metal and a chemical reaction that breaks down the TiH2 to release hydrogen. The expanding hydrogen bubbles create voids within the molten metal, and upon solidification of the metal, a closed cell metal foam results that closely conforms to the shape of the hollow structure to provide a light-weight and high strength reinforcement of the hollow structure.
However, the afore-described heating of the hollow structure may soften or cause a distortion of the hollow structure. Also the heating of the entire hollow structure may be disadvantageous as significant time may be needed to heat and then cool off the hollow structure. Furthermore, the heating of the mixture from the outside may permit the premature gassing of the foaming agent.
Thus it would be desirable to provide alternative methods for the in-situ foaming of a powder metal within a hollow structure.